JAVA - Fractal JPanel

 

package fractalpael;

import java.awt.Color;

import java.awt.Dimension;

import java.awt.Graphics;

import java.awt.Graphics2D;

import java.awt.image.BufferedImage;

import javax.swing.JComponent;

import javax.swing.JPanel;

import javax.swing.JFrame;

public class FractalPanel extends JPanel {

    final FractalSquare square = new FractalSquare(450, 350);

    public FractalPanel() {

        add(square);

    }

    public static void main(String[] args) {

        FractalPanel fractalPanel = new FractalPanel();

        JFrame frame = new JFrame();

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame.add(fractalPanel);

        frame.pack();

        frame.setVisible(true);

        Thread squareThread = new Thread(() -> {

            try {

                fractalPanel.square.render();

            } catch (InterruptedException e) {

                System.err.println("Interrupted");

            }

        });

        squareThread.start();

    }

}

class Fractal extends JComponent {

    final BufferedImage image;

    final Graphics2D offscreenGraphics;

    public Fractal(int width, int height) {

        setPreferredSize(new Dimension(width, height));

        image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

        offscreenGraphics = image.createGraphics();

    }

    // Copy the offscreen image to the main graphics context

    public void paint(Graphics g) {

        Graphics2D g2 = (Graphics2D) g;

        synchronized (image) { // synchronize with the render thread

            g2.drawImage(image, 0, 0, null);

        }

    }

}

class FractalSquare extends Fractal {

    public FractalSquare(int width, int height) {

        super(width, height);

    }

    public void render() throws InterruptedException {

        drawSquares(getWidth() / 2, getHeight() / 2, 100, 7);

    }

    public void drawSquares(int x, int y, int side, int size) throws InterruptedException {

        // Sleep for 10ms between frames

        Thread.sleep(10);

        if (size > 2) {

            size--;

            synchronized (image) { // synchronize with the draw thread

                offscreenGraphics.setColor(Color.BLUE);

                System.out.printf("Filling [%d, %d, %d, %d]\n", x - side / 2, y - side / 2, side, side);

                offscreenGraphics.fillRect(x - side / 2, y - side / 2, side, side);

            }

            // Tell Swing that we've updated the image and it needs to be redrawn

            repaint();

            side = side / 2;

            x = x - side;

            y = y - side;

            drawSquares(x, y, side, size);

            drawSquares(x + side * 2, y, side, size);

            drawSquares(x, y + side * 2, side, size);

            drawSquares(x + side * 2, y + side * 2, side, size);

        }

    }

}